I have an issue here. I was able to add all the necessary radio buttons on the VisualForce page for a Core Values  object. When I go to the page, it shows: Content cannot be displayed: Id value 00128000002k7Df is not valid for the Core_Values__c standard controller.

Here's the code.

<apex:page standardController="Core_Values__c">
<style type="text/css">
input[type="radio"]:checked {
    background-image: url("http://throwingthebowlines.com/wp-content/uploads/2013/12/checkbox.png");
}
        input[type="radio"]:checked+label{ color:red; font-weight:bold; }
    </style>

      <apex:form >
      <apex:pageBlock >
      <apex:pageblocksection columns="1" title="Core Values">
      <apex:selectRadio label="HSE" value="{!Core_Values__c.HSE__c}" border="1">
      <apex:selectOption itemLabel="Excellent" itemValue="6"/>
      <apex:selectOption itemLabel="Very Good" itemValue="5"/>
      <apex:selectOption itemLabel="Good" itemValue="4"/>
      <apex:selectOption itemLabel="Average" itemValue="3"/>
      <apex:selectOption itemLabel="Fair" itemValue="2"/>
      <apex:selectOption itemLabel="Poor" itemValue="1"/>
      </apex:selectRadio>
      
      <apex:selectRadio label="Professionalism & Integrity" value="{!Core_Values__c.Professionalism_Integrity__c}" border="1">
      <apex:selectOption itemLabel="Excellent" itemValue="6"/>
      <apex:selectOption itemLabel="Very Good" itemValue="5"/>
      <apex:selectOption itemLabel="Good" itemValue="4"/>
      <apex:selectOption itemLabel="Average" itemValue="3"/>
      <apex:selectOption itemLabel="Fair" itemValue="2"/>
      <apex:selectOption itemLabel="Poor" itemValue="1"/>
      </apex:selectRadio>
      
      <apex:selectRadio label="Quality / Accuracy" value="{!Core_Values__c.Quality_Accuracy__c}" border="1">
      <apex:selectOption itemLabel="Excellent" itemValue="6"/>
      <apex:selectOption itemLabel="Very Good" itemValue="5"/>
      <apex:selectOption itemLabel="Good" itemValue="4"/>
      <apex:selectOption itemLabel="Average" itemValue="3"/>
      <apex:selectOption itemLabel="Fair" itemValue="2"/>
      <apex:selectOption itemLabel="Poor" itemValue="1"/>
      </apex:selectRadio>
      
      <apex:selectRadio label="Technology / Innovation" value="{!Core_Values__c.Technology_Innovation__c}" border="1">
      <apex:selectOption itemLabel="Excellent" itemValue="6"/>
      <apex:selectOption itemLabel="Very Good" itemValue="5"/>
      <apex:selectOption itemLabel="Good" itemValue="4"/>
      <apex:selectOption itemLabel="Average" itemValue="3"/>
      <apex:selectOption itemLabel="Fair" itemValue="2"/>
      <apex:selectOption itemLabel="Poor" itemValue="1"/>
      </apex:selectRadio>
      
      <apex:selectRadio label="Timeliness" value="{!Core_Values__c.Timeliness__c}" border="1">
      <apex:selectOption itemLabel="Excellent" itemValue="6"/>
      <apex:selectOption itemLabel="Very Good" itemValue="5"/>
      <apex:selectOption itemLabel="Good" itemValue="4"/>
      <apex:selectOption itemLabel="Average" itemValue="3"/>
      <apex:selectOption itemLabel="Fair" itemValue="2"/>
      <apex:selectOption itemLabel="Poor" itemValue="1"/>
      </apex:selectRadio>
      
      <apex:selectRadio label="Value for Money" value="{!Core_Values__c.Value_for_Money__c}" border="1">
      <apex:selectOption itemLabel="Excellent" itemValue="6"/>
      <apex:selectOption itemLabel="Very Good" itemValue="5"/>
      <apex:selectOption itemLabel="Good" itemValue="4"/>
      <apex:selectOption itemLabel="Average" itemValue="3"/>
      <apex:selectOption itemLabel="Fair" itemValue="2"/>
      <apex:selectOption itemLabel="Poor" itemValue="1"/>
      </apex:selectRadio>
      
      </apex:pageblocksection>
      </apex:pageBlock>
      </apex:form>     
</apex:page>